Start walking the graph based on inputs.

lib/sibyl/graph.rb

@@ -29,6 +29,16 @@ def validate!
       raise InvalidGraph.new(e)
     end
 
+    def at(inputs)
+      step = @first_step
+      context = OpenStruct.new
+      inputs.each do |input|
+        result = step.compute(input, context)
+        step = @steps_by_name[result]
+      end
+      step
+    end
+
     def l10n_keys
       @steps.inject([]) { |keys, step|
         keys + step.l10n_keys

test/graph_test.rb

@@ -19,4 +19,22 @@ def graph(source)
 
     assert_equal expected, g.metadata
   end
+
+  it "should walk the nodes according to inputs" do
+    g = graph(%{
+      step multiple "Yes or no?"
+        option yes -> "How old are you?"
+        option no -> "Whatever"
+      step number "How old are you?"
+        go ->
+          if { input > 18 } -> "Adult"
+          otherwise -> "Child"
+      outcome "Whatever"
+      outcome "Adult"
+      outcome "Child"
+    })
+
+    assert_equal "How old are you?", g.at(["yes"]).name
+    assert_equal "Adult", g.at(["yes", 19]).name
+  end
 end